“There is a gap with information sharing at a higher level while there are still opportunities to intervene in the planning of these terrorist events,” Edward F. Davis III testified before the Senate Homeland Security and Governmental Affairs Committee. He urged lawmakers to write into the task force’s mission a requirement that information be shared.

The comment highlighted what lawmakers heard from federal and local officials as the central problem in the otherwise well-coordinated response to the April 15 bombings at the race’s finish line. The twin bombings killed three people and wounded more than 260.

Communications among agencies, as well as over cellphone lines, were problematic, officials told House and Senate committee reviewing the first successful terrorist bombing since the attacks of Sept. 11, 2001.

The chairman of the Homeland Security Committee complained that the FBI, the lead investigative agency in the bombing, had refused to attend. Questions linger about what the FBI knew in advance that might have helped prevent the horror.

“It is this committee’s responsibility find out how we did not see it coming,” said Rep. Michael McCaul, R-Texas. “We are going to find out what happened, what went wrong, and how to fix it.”

Experts testifying in the Senate said Boston’s response actually was exemplary, in part because the city had years ago built relationships and disaster plans among law enforcement, medical personnel and other responders. They urged Congress to support similar efforts in other cities large and small.

“People are on a first name basis” in Boston’s responder community, Richard Serino, deputy administrator for the Federal Emergency Management Agency, told senators. “The medical community has been linked in with public safety for years, not just since 2001.”

Arthur L. Kellermann, a doctor and analyst for the RAND Corporation, said Boston’s personnel had studied the way that their counterparts in London, Madrid and elsewhere had handled terrorist attacks.

“Boston’s responders were both lucky and good, that’s why so many victims survived,” Kellermann said. “They were prepared to do a great job ... everyone knew what to do. That’s how disaster plans work.”

Davis agreed, but said the memorandum of understanding for the Joint Terrorism Task Force, a partnership between federal and local law enforcement, should more specifically require threat information sharing on a routine basis with local police forces. Davis said that in the aftermath of the bombing, the FBI improved information sharing but that more needs to be done

The former head of the National Counterterrorism Center agreed that the task force rules make it hard to share information. Michael Leiter also told the House committee that better training is needed for law enforcement officials to be able to recognize radicalization among Americans.

Davis also said cellphone service in Boston was overloaded immediately after the attack.

Phones “were rendered completely useless as a means of communication at the scene,” he said, adding that “satellite phone technology is not effective for indoor command posts and communication across multiple bodies.”

Davis said law enforcement needs “a secure bandwidth in a public safety spectrum dedicated exclusively to public safety use now, as it is the only way to communicate during an event of this magnitude.”

The hearings took place as the sole surviving suspect was set to be arraigned Wednesday afternoon. Dzhokhar Tsarnaev was to appear Wednesday in federal court in Boston, charged with using a weapon of mass destruction in the bombings.